Survival Tip #244
5-Speed Bike
Think of yourself like a 5-speed bike. Every gear has a purpose. Some will take your farther per stroke, others will make your turnover easier for the climbs. Each of these is a different tool you can use to maximize the efficiency of the bike. You need to train to be able to use all of your speeds. There might need to be a time where a six minute mile is the different between life or death, but another occasion might require you to maintain a thirty minute mile for a hundred miles. Train yourself to be able to use every skill and talent you can muster and know when to use them.
Justin Kassab 
But before you start, prudently pump up the tires, check the brakes, and remember that everyone gets there in the end with the fastest usually the most exhausted at the other end.
Personally I keep in third the whole time.
Getting there, still smiling (and capable of coherent speech).